SSH Remote Shell with Multiple Commands

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Demonstrates running several commands one after another in a single remote shell session, retrieving each command's output separately. No PTY is requested, so each command is followed by an echoed marker that signals where its output ends.

Background: Interleaving commands and reads in one shell requires a way to know where each command's output stops. An interactive session would use the shell prompt, but without a PTY the shell is non-interactive and never prints one — so the dependable technique is to append echo SOME_MARKER to each command and read up to that marker. Retrieving the text also clears the receive buffer, which matters here: if a marker were left buffered, the next receive would match it immediately and return the wrong output.

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bool success = false;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Demonstrates running several commands one after another in a single remote shell session,
//  retrieving each command's output separately.
//  
//  No PTY is requested, so the shell runs non-interactively and never prints a command prompt.
//  Because there is no prompt to synchronize on, each command is followed by an "echo" of a
//  unique marker, and the output is read up to that marker.

Chilkat.Ssh ssh = new Chilkat.Ssh();

string hostname = "ssh.example.com";
int port = 22;
success = ssh.Connect(hostname,port);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
string password = "mySshPassword";

success = ssh.AuthenticatePw("mySshLogin",password);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

int channelNum = ssh.OpenSessionChannel();
if (channelNum < 0) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
//  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
//  echo typed commands back, and skips interactive login scripts.  The output is therefore
//  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
//  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
success = ssh.SendReqShell(channelNum);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
//  which means no limit -- without it, this call waits forever if the received data never
//  contains a match.
ssh.ReadTimeoutMs = 15000;

bool caseSensitive = true;

//  ---- 1st command: change directory ----
success = ssh.ChannelSendString(channelNum,"cd /tmp; echo END_OF_CMD_1\n","utf-8");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

success = ssh.ChannelReceiveUntilMatch(channelNum,"END_OF_CMD_1","utf-8",caseSensitive);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  Retrieving the text also clears the receive buffer, which matters: if the next marker were
//  left in the buffer, the following receive would match immediately.
string cmdOutput = ssh.GetReceivedText(channelNum,"utf-8");
if (ssh.LastMethodSuccess == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

Debug.WriteLine(cmdOutput);

//  ---- 2nd command: directory listing ----
success = ssh.ChannelSendString(channelNum,"ls; echo END_OF_CMD_2\n","utf-8");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

success = ssh.ChannelReceiveUntilMatch(channelNum,"END_OF_CMD_2","utf-8",caseSensitive);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

cmdOutput = ssh.GetReceivedText(channelNum,"utf-8");
if (ssh.LastMethodSuccess == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

Debug.WriteLine(cmdOutput);

//  ---- 3rd command: long listing, then finish the session ----
success = ssh.ChannelSendString(channelNum,"ls -l\n","utf-8");
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

//  No more input will be sent.
success = ssh.ChannelSendEof(channelNum);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

success = ssh.ChannelReceiveToClose(channelNum);
if (success == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

cmdOutput = ssh.GetReceivedText(channelNum,"utf-8");
if (ssh.LastMethodSuccess == false) {
    Debug.WriteLine(ssh.LastErrorText);
    return;
}

Debug.WriteLine(cmdOutput);

ssh.Disconnect();